Refractive errors

Question 1

What is a refractive error?

Name types.

Answer 1

A problem in which light does not focus accurately onto the retina

Causing poor vision

Due to a problem with the shape of the eye, or the refraction of light by the lens or cornea.

1. Hyperopia: long-sighted
2. Myopia: short-sighted
3. Astigmatism
4. Presbyopia

Question 2

What are hyperopia and myopia?

Answer 2

Hyperopia:

• long-sighted
• can see far away clearly
• struggle to see close-up

Myopia:

• short-sighted
• can see close up
• struggle to see far away

Question 3

Pathophysiology of hyperopia?

Causes?

Answer 3

Long-sighted

Light is focussed behind, instead of on, the retina

• Close-up vision is blurry
• Far away vision is fine

Causes:

• axial: eyeball too short
• refractive: mishapen lens or cornea

Question 4

What is the difference between axial and refractive hyperopia?

Answer 4

Axial = the problem is the eyeball being too short

Refractive = the problem is the refraction mishapen lens or cornea affecting refraction

Question 5

Management of refractive errors?

Answer 5

Glasses / contact lenses which change refraction of light so it lands on the retina

Hyperopia: + prescription
Myopia: - prescription

Surgery: which changes shape of cornea, changing refraction of light

Question 6

Signs and symptoms of refractive errors?

Answer 6

Blurry vision
Eye strain
Headaches

Difficulty seeing with both eyes
Difficulty with depth perception

Question 7

Pathophysiology of myopia?

Causes?

Answer 7

Short-sighted

Light focuses in front of, instead of on, the retina

• Far-away vision is blurry
• Close-up vision is fine

Question 8

What is presbyopia?

Answer 8

Loss of lens elasticity with age

Causing light to be focused behind the retina rather than on it.

It causes long-sightedness
(vision blurry close-up, but fine far away)

Question 9

What is astigmatism?
Pathophysiology?
Causes?

Answer 9

A type of refractive error where light is not focused evenly on the retina

Distorted/blurry vision at all distances

Pathophysiology: irregular curvature of cornea, or abnormalities in lens.

Causes: genetic

Question 10

What is the term used to describe misaligned eyes?

Answer 10

Strabismus

Question 11

What is strabismus?

What are the types?

Answer 11

Condition in which the eyes do not properly align with eachother when looking at an object

Esotropia: deviates inwards
Exotropia: deviates outwards
Hypotropia: deviates downwards
Hypertropia: deviates upwards

Question 12

What are some causes of strabismus?

Answer 12

Idiopathic

Brain disorder: cerebral palsy, Down’s, SOL

Stroke

Grave’s disease

Nerve palsy (III, IV, VI)